Icariin induces osteoblast proliferation, differentiation and mineralization through estrogen receptor-mediated ERK and JNK signal activation

Engineered three-dimensional scaffolds for enhanced bone regeneration in osteonecrosis

Osteonecrosis, which is typically induced by trauma, glucocorticoid abuse, or alcoholism, is one of the most severe diseases in clinical orthopedics. Osteonecrosis often leads to joint destruction, and arthroplasty is eventually required. Enhancement of bone regeneration is a critical management strategy employed in osteonecrosis therapy. Bone tissue engineering based on engineered three-dimensional (3D) scaffolds with appropriate architecture and osteoconductive activity, alone or functionalized with bioactive factors, have been developed to enhance bone regeneration in osteonecrosis. In this review, we elaborate on the ideal properties of 3D scaffolds for enhanced bone regeneration in osteonecrosis, including biocompatibility, degradability, porosity, and mechanical performance. In addition, we summarize the development of 3D scaffolds alone or functionalized with bioactive factors for accelerating bone regeneration in osteonecrosis and discuss their prospects for translation to clinical practice.

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Engineered three-dimensional scaffolds boost bone regeneration in osteonecrosis.

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The ideal properties of three-dimensional scaffolds for osteonecrosis treatment are discussed.

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Bioactive factors-functionalized three-dimensional scaffolds are promising bone regeneration devices for osteonecrosis management.

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The challenges and opportunities of engineered three-dimensional scaffolds for osteonecrosis therapy are predicted.

Icariin controlled release on a silk fibroin/mesoporous bioactive glass nanoparticles scaffold for promoting stem cell osteogenic differentiation

The treatment of bone defects caused by various reasons is still a major problem in orthopedic clinical work. Many studies on osteogenic implant materials have used various biologically active factors such as osteogenic inducers, but these biologically active factors have various side effects. Therefore, in this study, silk fibroin (SF) was used as a scaffold material, mesoporous bioactive glass nanoparticles (MBGNs) as a sustained release carrier, and the traditional Chinese drug icariin (ICA) was loaded to promote bone formation. The experiments in this study have proven that SF/MBGNs-ICA scaffolds can successfully load and release ICA for a long time, and the sustained-release ICA can promote the proliferation and differentiation of BMSCs for a long time. This controlled-release ICA organic/inorganic two-component scaffold material is expected to become a new bone grafting solution.

Modulation of bone turnover aberration: A target for management of primary osteoporosis in experimental rat model

Osteoporosis is a skeletal degenerative disease characterised by abnormal bone turnover with scant bone formation and overabundant bone resorption. The present approach was intended to address the potency of nanohydroxyapatite (nHA), chitosan/hydroxyapatite nanocomposites (nCh/HA) and silver/hydroxyapatite nanoparticles (nAg/HA) to modulate bone turnover deviation in primary osteoporosis induced in the experimental model. Characterisation techniques such as TEM, zeta-potential, FT-IR and XRD were used to assess the morphology, the physical as well as the chemical features of the prepared nanostructures. The in vivo experiment was conducted on forty-eight adult female rats, randomised into 6 groups (8 rats/group), (1) gonad-intact, (2) osteoporotic group, (3) osteoporotic + nHA, (4) osteoporotic + nCh/HA, (5) osteoporotic + nAg/HA and (6) osteoporotic + alendronate (ALN). After three months of treatment, serum sclerostin (SOST), bone alkaline phosphatase (BALP) and bone sialoprotein (BSP) levels were quantified using ELISA. Femur bone receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) and cathepsin K (CtsK) mRNA levels were evaluated by quantitative RT-PCR. Moreover, alizarin red S staining was applied to determine the mineralisation intensity of femur bone. Findings in the present study indicated that treatment with nHA, nCh/HA or nAg/HA leads to significant repression of serum SOST, BALP and BSP levels parallel to a significant down-regulation of RANKL and CtsK gene expression levels. On the other side, significant enhancement in the calcification intensity of femur bone has been noticed. The outcomes of this experimental setting ascertained the potentiality of nHA, nCh/HA and nAg/HA as promising nanomaterials in attenuating the excessive bone turnover in the primary osteoporotic rat model. The mechanisms behind the efficacy of the investigated nanostructures involved the obstacle of serum and tissue indices of bone resorption besides the strengthening of bone mineralisation.

Pilose antler peptide promotes osteoblast proliferation, differentiation and mineralization via the insulin signaling pathway

Osteoporosis is a severe bone disease characterized by a decrease in the density and structure of bones, with high risks of fractures. Pilose antler peptide (PAP), extracted and purified from deer antlers, can promote regeneration and fracture healing, and strengthen sinews and bone. To determine whether PAP can promote osteoblast development and to elucidate the molecular mechanisms underlying its functions, the present study investigated the effects of PAP on osteoblast proliferation, differentiation and mineralization, and the role of the insulin signaling pathway using MTT assay, alkaline phosphatase activity assay, western blot analysis and reverse transcription-quantitative PCR. The present results suggested that PAP promoted osteoblast proliferation, differentiation and mineralization in vitro via the insulin signaling pathway. The effect of PAP on insulin signaling in osteoblasts may be mediated via the ERK pathway and partially by the PI3K/Akt pathway. The present results indicated that PAP could potentially be developed as an alternative treatment strategy for bone diseases related to diabetes characterized by insulin signaling impairment.

Icariin alleviates hypoxia-induced damage in MC3T3-E1 cells by downregulating TALNEC2

Osteonecrosis is a harmful musculoskeletal disease. We aim to detect the effects of icariin (ICA) in MC3T3-E1 cell. MC3T3-E1 cell was pretreated with ICA and was subjected to hypoxia stimuli. The tumor-associated long noncoding RNA expressed on chromosome 2 (TALNEC2) overexpression or silencing vectors (pTALNEC2 or si-TALNEC2) was utilized for MC3T3-E1 cell transfection. Viability and apoptosis rate were individually tested by cell counting kit-8 and Annexin V-fluorescein isothiocyanate/propidium iodide kit untied with flow cytometry. The alkaline phosphatase activity (ALP) activity was tested through ALP assay. The quantitative reverse transcription PCR or Western blot was performed for elements detection at the RNA or protein level. Hypoxia treatment induced viability inhibition and CyclinD1 reduction, but elevation of p53 and p16. It also promoted apoptosis by increasing apoptotic cells, Bax, and cleaved-poly ADP-ribose polymerase but decreasing Bcl-2. Also, hypoxia stimuli restrained ALP activity, and osteopontin, osteocalcin, and Runt-related transcription factor 2 expression. Those effects caused by hypoxia stimuli were all reversed by ICA. TALNEC2 was downregulated by ICA, whose impacts were subsequently abolished by pTALNEC2. Silencing TALNEC2 displayed similar effects with ICA. But the apoptosis was not affected by si-TALNEC2. ICA blocked ste20-related proline/alanine-rich kinase/c-Jun N-terminal kinase (SPAK/JNK) but triggered phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway in MC3T3-E1 cell by suppressing TALNEC2. ICA relieved hypoxia-stimulated damage by restraining TALNEC2 through blocking SPAK/JNK and triggering PI3K/AKT/mTOR in the MC3T3-E1 cell.

Therapeutic Anabolic and Anticatabolic Benefits of Natural Chinese Medicines for the Treatment of Osteoporosis

Osteoporosis is a bone disease characterized by increasing osseous fragility and fracture due to the reduced bone mass and microstructural degradation. Primary pharmacological strategies for the treatment of osteoporosis, hormone replacement treatment (HRT), and alendronate therapies may produce adverse side-effects and may not be recommended for long-term usage. Some classic and bone-specific natural Chinese medicine are very popularly used to treat osteoporosis and bone fracture effectively in clinical with their potential value in bone growth and development, but with few adverse side-effects. Current evidence suggests that the treatments appear to improve bone metabolism and attenuate the osteoporotic imbalance between bone formation and bone resorption at a cellular level by promoting osteoblast activity and inhibiting the effects of osteoclasts. The valuable therapies might, therefore, provide an effective and safer alternative to primary pharmacological strategies. Therefore, the purpose of this article is to comprehensively review these classic and bone-specific drugs in natural Chinese medicines for the treatment of osteoporosis that had been deeply and definitely studied and reported with both bone formation and antiresorption effects, including Gynochthodes officinalis (F.C.How) Razafim. & B.Bremer (syn. Morinda officinalis F.C.How), Curculigo orchioides Gaertn., Psoralea corylifolia (L.) Medik Eucommia ulmoides Oliv., Dipsacus inermis Wall. (syn. Dipsacus asperoides C.Y.Cheng & T.M.Ai), Cibotium barometz (L.) J. Sm., Velvet Antler, Cistanche deserticola Ma, Cuscuta chinensis Lam., Cnidium monnieri (L.) Cusson, Epimedium brevicornum Maxim, Pueraria montana (Lour.) Merr. and Salvia miltiorrhiza Bunge., thus providing evidence for the potential use of alternative Chinese medicine therapies to effectively treat osteoporosis.

Prenylflavonoid Icariin Induces Estrogen Response Element-Independent Estrogenic Responses in a Tissue-Selective Manner

Icariin, a flavonoid phytoestrogen derived from Herba epimedii, has been reported to exert estrogenic effects in bone and activate phosphorylation of estrogen receptor (ER) α in osteoblastic cells. However, it is unclear whether icariin selectively exerts estrogenic activities in bone without inducing undesirable effects in other estrogen-sensitive tissues. The present study aimed to investigate the tissue-selective estrogenic activities of icariin in estrogen-sensitive tissues in vivo and in vitro. Long-term treatment with icariin effectively prevented bone of ovariectomized (OVX) rats from estrogen deficiency–induced osteoporotic changes in bone structure, bone mineral density, and trabecular properties. Moreover, icariin regulated the transcriptional events of estrogen-responsive genes related to bone remodeling and prevented dopaminergic neurons against OVX-induced changes by rescuing expression of estrogen-regulated tyrosine hydroxylase and dopamine transporter in the striatum. Unlike estrogen, icariin did not induce estrogenic effects in the uterus and breast in mature OVX rats or immature CD-1 mice. In vitro studies demonstrated that icariin exerted estrogen-like activities and regulated the expression of estrogen-responsive genes but did not induce estrogen response element–dependent luciferase activities in ER-positive cells. Our results support the hypothesis that icariin, through its distinct mechanism of actions in activating ER, selectively exerts estrogenic activities in different tissues and cell types.

Icariin promotes osteogenic differentiation by suppressing Notch signaling

Osteoporosis is a bone disease characterized by microarchitectural deterioration, low bone mass, and increased risk of fractures. Icariin (ICA), an active flavonoid glucoside isolated from Herba epimedii (HEF), is a potent stimulator of osteogenic differentiation and has potential applications for preventing bone loss in postmenopausal women. However, the molecular mechanism underlying the osteogenic effect of ICA has not yet been fully elucidated. In this study, we report that ICA treatment significantly elevated gene expression of osteogenic markers and increased alkaline phosphatase (ALP) activity in MC3T3-E1 and C3H10T1/2 cells. RNA sequencing revealed that the expression of several genes involved in the Notch pathway was decreased following ICA treatment. Real-time PCR further demonstrated that the mRNA levels of Notch ligands Jagged-1 (Jag1), lunatic fringe (Lfng), and Notch signaling downstream target gene Hey-1 were significantly decreased following ICA treatment. In addition, we found that constitutive activation of Notch signaling through overexpression of the intracellular domain of Notch (NICD) fully blocked ICA-induced osteoblast differentiation. Moreover, inhibiting Notch signaling with DAPT markedly enhanced osteogenic differentiation following ICA treatment. We found that the mRNA levels of Notch pathway molecules (Lfng, Notch1, Rbpjk and Nfatc1) were increased in ovariectomized (OVX) mice, and administration of ICA significantly decreased the expression of these genes. Our results suggest that ICA promotes osteogenic differentiation in vitro and alleviates osteoporosis in vivo through inhibition of the Notch signaling pathway.

Icariin Promotes the Osteogenic Action of BMP2 by Activating the cAMP Signaling Pathway

Icariin (ICA) is the main active flavonoid glucoside from herbs of the genus Epimedium; in traditional Chinese medicine, these herbs have long been prescribed for the treatment of bone fractures and osteoporosis. Several studies have shown that treatment with ICA can increase osteogenic differentiation and reduce bone loss in vivo and in vitro. However, the definite signaling pathway of this osteogenic effect remains unclear. In this study, we selected bone morphogenetic protein 2 (BMP2)-induced osteoblastic differentiation of multipotent mesenchymal progenitor C2C12 cells as a model of osteoblast differentiation. We investigated the effects of ICA on C2C12 cells osteogenic differentiation and the underlying molecular mechanisms. We found that ICA could enhance BMP2-mediated osteoblastic differentiation of C2C12 cells in a dose-dependent manner. Treatment with ICA activated the cAMP/PKA/CREB signaling axis in a time-dependent manner. Blocking cAMP signaling using the PKA selective inhibitor H89 significantly inhibited the stimulatory effect of ICA on osteogenesis. Therefore, the osteoinductive potential and the low cost of ICA indicate that it is a promising alternative treatment or promoter for enhancing the therapeutic effects of BMP2.

The naturally derived small compound Osthole inhibits osteoclastogenesis to prevent ovariectomy-induced bone loss in mice

OBJECTIVE

This study was to determine the bone protective effects and underlying mechanisms of Osthole (OT) in ovariectomized (OVX) mice. We found that the inhibitory effects of OT on receptor activator of nuclear factor kappa-B ligand (RANKL)-activated osteoclastogenesis are responsible for its bone protective effects in OVX mice.

METHODS

Eight-week-old mice were ovariectomized and OT (10 mg/kg/d) was intraperitoneally administrated to OVX mice 7 days after the surgery and were sacrificed at the end of the 3 months. Osteoclasts were generated from primary bone marrow macrophages (BMMs) to investigate the inhibitory effects of OT. The activity of RANKL-activated signaling was simultaneously analyzed in vitro and in vivo using immunohistochemistry, Western blot, and PCR assays.

RESULTS

OT dose dependently inhibited RANKL-mediated osteoclastogenesis in BMM cultures. OT administration attenuated bone loss (mg Ha/cm: 894.68 ± 33.56 vs 748.08 ± 19.51, P < 0.05) in OVX mice. OT inhibits osteoclastogenesis (Oc.N/per view area: 72 ± 4.3 vs 0.8 ± 0.4, P < 0.05) and bone resorption activity (bone resorbed percentages %, 48.56 ± 7.25 vs 3.25 ± 1.37, P < 0.05) from BMMs. Mechanistically, OT inhibited the expressions of nuclear factor of activated T-cells c1 (NFATc1) and c-Fos. Moreover, OT suppressed the expression of RANKL-induced osteoclast marker genes, including matrix metalloproteinase 9 (MMP9), Cathepsin K (Ctsk), tartrate-resistant acid phosphatase (TRAP), and carbonic anhydrase II (Car2).

CONCLUSIONS

OT inhibits RANKL-mediated osteoclastogenesis and prevents bone loss in OVX mice. Our findings revealed that OT is a potential new drug for treating postmenopausal osteoporosis.

Bioactive molecule Icariin inhibited proliferation while enhanced apoptosis and autophagy of rat airway smooth muscle cells in vitro

Icariin is the main active compound extracted from epimedium Flavonoids (EFs) and involved in regulation of cell behaviors (proliferation, apoptosis, and autophagy etc.) for many cell types, but the effect of Icariin on airway smooth muscle cells (ASMCs) is still unknown. The aim of the present study is to examine the role of Icariin on rat ASMCs proliferation, apoptosis and autophagy. CKK8 assay showed that Icariin inhibited rat ASMCs growth in dose-time-dependent manner, and the flow cytometry assay showed that the Icariin interfered with ASMCs cell cycle, when treated with Icariin, S phase shortened while G2 phase extended, cyclin E1 and cyclinA1 gene and protein expression decreased. Next apoptosis was detected, Flow cytometry and TdTmediated dUTP Nick-End Labeling (TUNEL) assay showed that Icariin promoted ASMCs apoptosis, and enhanced apoptosis protein cleaved-caspase-3 expression. Finally, it was found Icariin induced rat ASMCs autophagy, with enhancement expression of autophagy marker LC3 II. In conclusion, Icariin inhibited ASMCs proliferation while promoted apoptosis and autophagy, revealing its potential role in treatment of airway remodeling in asthma.

Dracohodin Perochlorate Stimulates Fibroblast Proliferation via EGFR Activation and Downstream ERK/CREB and PI3K/Akt/mTOR Pathways In Vitro

In recent years, an increasing number of natural plant extracts have been determined to be potential drugs for various illnesses. In this study, we investigated the effects of dracorhodin perchlorate (DP) on fibroblast proliferation, which is crucial for wound healing. Cell proliferation assays were performed by different concentrations of DP, and the cell viability was detected by CCK-8 kits. After DP treatment for 24 h, the cell cycle was checked by flow cytometer. EGFR and downstream signaling pathways ERK1/2 and PI3K were examined with DP treatment by western blot. We further determined the effects of the related inhibitors on DP-induced relative protein phosphorylation and cell proliferation. The results showed that 3 μg/mL of DP promoted cell proliferation most significantly at treatment lengths of 24 h, and the percentage of cells in the S + G2 phase increased compared to those of the control group. In western blot detection, we found that DP significantly upregulated EGFR phosphorylation and activated the downstream ERK/CREB and PI3K/Akt/mTOR signaling pathway. Moreover, the results also showed that AG1478 abolished DP-induced relative protein activation and cell proliferation. When U0126 or LY294002 pretreated cells alone, DP-induced p-ERK or p-PI3K downstream proteins and cell proliferation were suppressed compared to those of the control group, but EGFR was not affected. In addition, ICG001 and BEZ235 collectively eliminated DP-induced fibroblast proliferation. Our findings suggest that DP-promoted fibroblast proliferation is stimulated by p-EGFR-induced activation of the ERK1/2-CREB and PI3K/Akt/mTOR pathways. Our present study explored the mechanism of DP-promoted fibroblast proliferation and provided a new basis for wound healing.

Icariin-loaded porous scaffolds for bone regeneration through the regulation of the coupling process of osteogenesis and osteoclastic activity

Objective

Icariin (IC) promotes osteogenic differentiation, and it may be a potential small molecule drug for local application in bone regeneration. Icariin-loaded hydroxyapatite/alginate (IC/HAA) porous composite scaffolds were designed in this study for the potential application of the sustainable release of icariin and subsequent bone regeneration.

Methods

An icariin-loaded hydroxyapatite/alginate porous composite scaffold was prepared and characterized by SEM and HPLC for morphology and release behavior, respectively. The mechanical properties, degradation in PBS and cytotoxicity on BMSCs were also evaluated by MTT assay, compression strength and calculation of weight remaining ratio, respectively. Rabbit BMSCs were cocultured with IC/HAA scaffolds, and ALP activity and Alizarin Red staining were performed to evaluate osteogenic differentiation induction. The mRNA and protein expression level of an osteogenic gene was detected by RT-PCR and Western blotting, respectively. In vivo animal models of critical bone defects in the radius of rabbit were used. Four and 12 weeks after the implantation of IC/HAA scaffolds in the bone defect, radiographic images of the radius were obtained and scored by using the Lane and Sandhu X-ray scoring system. Tissue samples were also evaluated using H&E and Masson staining, and an osteogenic gene and Wnt signaling pathway genes were detected.

Results

A hydroxyapatite/alginate (HAA) porous composite scaffold-loaded icariin was fabricated using a freeze-drying method. Our data indicated that the icariin was loaded in alginate scaffold without compromising the macro/microstructure or mechanical properties of the scaffold. Notably, the IC/HAA promoted the proliferation of rBMSCs without exerting cytotoxicity on rBMSCs. In vivo, rabbit radius bone defect experiments demonstrated that the IC/HAA scaffold exhibited better capacity for bone regeneration than HAA, and IC/HAA upregulated the relative expression levels of an osteogenic gene and the Wnt signaling pathway genes. Most notably, the IC/HAA scaffold also inhibited osteoclast activity in vivo.

Conclusion

Our data suggests a promising application for the use of HAA scaffolds to load icariin and promote bone regeneration in situ through mediation of the coupling processes of osteogenesis induction and osteoclast activity inhibition.

Autologous Freeze-Dried, Platelet-Rich Plasma Carrying Icariin Enhances Bone-Tendon Healing in a Rabbit Model

BACKGROUND

Tendon-bone interface (TBI) injuries are common in sports activities. Owing to the limited regenerative ability of the TBI, its functional healing remains a difficulty in clinical practice. Icariin (ICA) provides strong stimulation for osteogenesis. Platelet-rich plasma (PRP) can be used as a carrier for bioactive molecules, although its ability to provide sustained release for such molecules needs improvement.

HYPOTHESIS

Freeze-dried PRP (FD-PRP) as a carrier for ICA can provide sustained release of ICA into the tendon-bone (T-B) healing site, thus accelerating T-B healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 84 New Zealand rabbits with partial patellectomy in the hindlimb were randomly allocated into 3 different treatments: ICA incorporated with FD-PRP (ICA/FD-PRP), FD-PRP alone (FD-PRP), or saline control (CTL). The rabbit patella-patellar tendon (PP) interfaces were postoperatively harvested at postoperative week 8 or 16 for gross, radiological, histological, and mechanical evaluations.

RESULTS

Our results showed that FD-PRP can act as a carrier for sustained release of ICA into the T-B healing site. Macroscopically, no signs of infection or osteoarthritis were shown in the regenerated PP interfaces, and the area of cartilaginous metaplasia in the FD-PRP and ICA/FD-PRP groups at postoperative week 16 was significantly larger than that of the CTL group (P < .05 for all). Radiologically, micro-computed tomography showed that new bone which formed at the healing site in the ICA/FD-PRP group was significantly increased, remodeled, and mineralized in comparison with the CTL group (P < .05 for all). Histologically, the ICA/FD-PRP group exhibited a significant native PP interface, as shown by the enlargement and remodeling of new bone, well-organized collagen fibers, and robust production of proteoglycans in the regenerated fibrocartilage. The mechanical strength of the regenerated PP interface was significantly improved in the ICA/FD-PRP group. Significantly higher failure load and stiffness were shown in the ICA/FD-PRP group compared with the CTL and FD-PRP groups, respectively (P < .05 for all).

CONCLUSION

FD-PRP is a suitable sustained-release carrier for ICA, and ICA/FD-PRP can provide sustained release of ICA into the T-B healing site, thus effectively accelerating T-B healing.

CLINICAL RELEVANCE

Findings of this study demonstrate the feasibility of using FD-PRP as a carrier for ICA to improve T-B healing and provide a foundation for future clinical application.

Mimicking growth factors: role of small molecule scaffold additives in promoting tissue regeneration and repair

The primary aim of tissue engineering scaffolds is to mimic the in vivo environment and promote tissue growth. In this quest, a number of strategies have been developed such as enhancing cell-material interactions through modulation of scaffold physico-chemical parameters. However, more is required for scaffolds to relate to the cell natural environment. Growth factors (GFs) secreted by cells and extracellular matrix (ECM) are involved in both normal repair and abnormal remodeling. The direct use of GFs on their own or when incorporated within scaffolds represent a number of challenges such as release rate, stability and shelf-life. Small molecules have been proposed as promising alternatives to GFs as they are able to minimize or overcome many shortcomings of GFs, in particular immune response and instability. Despite the promise of small molecules in various TE applications, their direct use is limited by nonspecific adverse effects on non-target tissues and organs. Hence, they have been incorporated within scaffolds to localize their actions and control their release to target sites. However, scanty rationale is available which links the chemical structure of these molecules with their mode of action. We herewith review various small molecules either when used on their own or when incorporated within polymeric carriers/scaffolds for bone, cartilage, neural, adipose and skin tissue regeneration.

Dual functional approaches for osteogenesis coupled angiogenesis in bone tissue engineering

Bone fracture healing is a multistep and overlapping process of inflammation, angiogenesis and osteogenesis. It is initiated by inflammation, causing the release of various cytokines and growth factors. It leads to the recruitment of stem cells and formation of vasculature resulting in the functional bone formation. This combined phenomenon is used by bone tissue engineers from past few years to address the problem of vasculature and osteogenic differentiation during bone regeneration. In this review, we have discussed all major studies reporting the dual functioning approach to promote osteogenesis coupled angiogenesis using various scaffolds. These scaffolds are broadly classified into four types based on the nature of their structural and functional components. The functionality of the scaffold is either due to the structural components or the loaded cargo which conducts or induces the coupled functionality. Dual delivery system for osteoinductive and angioinductive factors ensures the co-delivery of two different types of molecules to induce osteogenesis and angiogenesis. Single delivery scaffold for angioinductive and osteoinductive molecule releases single type of molecules which could induce both angiogenesis and osteogenesis. Osteoconductive scaffold consisted of bone constituents releases angioinductive factors. Osteoconductive and angioconductive scaffold composed of components which provide the native substrate features for osteogenesis and angiogenesis. This review article also discusses the studies highlighting the synergism of physico-chemical stimuli as dual functioning feature to enhance angiogenesis and osteogenesis simultaneously. In addition, this article covers one of the least discussed area of the bone regeneration i.e. 'cartilage formation as a median between angiogenesis and osteogenesis'.

Rehmanniae Radix Preparata suppresses bone loss and increases bone strength through interfering with canonical Wnt/β-catenin signaling pathway in OVX rats

Rehmanniae Radix Preparata (RRP) improves bone quality in OVX rats through the regulation of bone homeostasis via increasing osteoblastogenesis and decreasing osteoclastogenesis, suggesting it has a potential for the development of new anti-osteoporotic drugs.

INTRODUCTION

Determine the anti-osteoporotic effect of RRP in ovariectomized (OVX) rats and identify the signaling pathway involved in this process.

METHODS

OVX rats were treated with RRP aqueous extract for 14 weeks. The serum levels of tartrate-resistant acid phosphatase (TRAP), receptor activator of nuclear factor kappa-Β ligand (RANKL), alkaline phosphatase (ALP), and osteoprotegerin (OPG) were determined by ELISA. Bone histopathological alterations were evaluated by H&E, Alizarin red S, and Safranin O staining. Bone mineral density (BMD) and bone microstructure in rat femurs and lumbar bones were determined by dual-energy X-ray absorptiometry and micro-computed tomography. Femoral bone strength was detected by a three-point bending assay. The expression of Phospho-glycogen synthase kinase 3 beta (p-GSK-3β), GSK-3β, Dickkopf-related protein 1 (DKK1), cathepsin K, OPG, RANKL, IGF-1, Runx2, β-catenin, and p-β-catenin was determined by western blot and/or immunohistochemical staining.

RESULTS

Treatment of OVX rats with RRP aqueous extract rebuilt bone homeostasis demonstrated by increasing the levels of OPG as well as decreasing the levels of TRAP, RANKL, and ALP in serum. Furthermore, RRP treatment preserved BMD and mechanical strength by increasing cortical bone thickness and epiphyseal thickness as well as improving trabecular distribution in the femurs of OVX rats. In addition, RRP downregulated the expression of DKK1, sclerostin, RANKL, cathepsin K, and the ratio of p-β-catenin to β-catenin, along with upregulating the expression of IGF-1, β-catenin, and Runx2 and the ratio of p-GSK-3β to GSK-3β in the tibias and femurs of OVX rats. Echinacoside, jionoside A1/A2, acetoside, isoacetoside, jionoside B1, and jionoside B2 were identified in the RRP aqueous extract.

CONCLUSION

RRP attenuates bone loss and improves bone quality in OVX rats partly through its regulation of the canonical Wnt/β-catenin signaling pathway, suggesting that RRP has the potential to provide a new source of anti-osteoporotic drugs.

Astragalin Promotes Osteoblastic Differentiation in MC3T3-E1 Cells and Bone Formation in vivo

Astragalin (AG) is a biologically active flavonoid compound that can be extracted from a number of medicinal plants. However, the effects of AG on osteoblastic differentiation in mouse MC3T3-E1 cells and on bone formation in vivo have not been studied fully. In this study, we found that the activities of alkaline phosphatase (ALP) and mineralized nodules in MC3T3-E1 cells were both significantly increased after treatment with AG (5, 10, and 20 μM). Meanwhile, the mRNA and protein levels of osteoblastic marker genes in MC3T3-E1 cells after AG treatment were markedly increased compared with a control group. In addition, the levels of BMP-2, p-Smad1/5/9, and Runx2 were significantly elevated in AG-treated MC3T3-E1 cells. Moreover, we found that the protein levels of Erk1/2, p-Erk1/2, p38, p-p38, and p-JNK were also significantly increased in AG-treated MC3T3-E1 cells compared to those in the control group. Finally, in vivo experiments demonstrated that AG significantly promoted bone formation in an ovariectomized (OVX)-induced osteoporotic mouse model. This was evidenced by significant increases in the values of osteoblast-related parameters (BFR/BS, MAR, Ob.S/BS, and Ob.N/B.Pm) and bone histomorphometric parameters (BMD, BV/TV, Tb.Th, and Tb.N.) in OVX mice after AG treatment (5, 10, and 20 mg/kg). Collectively, these results demonstrated that AG may promote osteoblastic differentiation in MC3T3-E1 cells via the activation of the BMP and MAPK pathways and promote bone formation in vivo. These novel findings indicated that AG may be a useful bone anabolic agent for the prevention and treatment of osteoporosis.

Different duration of parathyroid hormone exposure distinctively regulates primary response genes Nurr1 and RANKL in osteoblasts

Parathyroid hormone (PTH) exerts dual effects, anabolic or catabolic, on bone when administrated intermittently or continuously, via mechanisms that remain largely unknown. PTH binding to cells induces PTH-responsive genes including primary response genes (PRGs). PRGs are rapidly induced without the need for de novo protein synthesis, thereby playing pivotal roles in directing subsequent molecular responses. In this study, to understand the role of PRGs in mediating osteoblastic cellular responses to PTH, we investigated whether various durations of PTH differentially induce PRGs in primary osteoblasts and MC3T3-E1. Nurr1 and RANKL, PRGs known for their anabolic and catabolic roles in bone metabolism respectively, presented distinctive transient vs. sustained induction kinetics. Corroborating their roles, maximum induction of Nurr1 was sufficiently achieved by brief PTH in as little as 30 minutes and continued beyond that, while maximum induction of RANKL was achieved only by prolonged PTH over 4 hours. Our data suggested distinctive regulatory mechanisms for Nurr1 and RANKL: PKA-mediated chromatin rearrangement for transcriptional regulation of both PRGs and ERK-mediated transcriptional regulation for RANKL but not Nurr1. Lastly, we classified PRGs into two groups based on the induction kinetics: The group that required brief PTH for maximum induction included Nur77, cox-2, and Nurr1, all of which are reported to play roles in bone formation. The other group that required prolonged PTH for maximum induction included IL-6 and RANKL, which play roles in bone resorption. Together, our data suggested the crucial role of PRG groups in mediating differential osteoblastic cellular responses to intermittent vs. continuous PTH. Continued research into the regulatory mechanisms of PKA and ERK for PRGs will help us better understand the molecular mechanisms underlying the dual effects of PTH, thereby optimizing the current therapeutic use of PTH for osteoporosis.

MicroRNA-497 inhibits multiple myeloma growth and increases susceptibility to bortezomib by targeting Bcl-2

Multiple myeloma (MM) is a common severe hematopoietic malignancy occuring in aged population. MicroRNA (miR)‑497 was previously reported to contribute to the apoptosis of other cell types, presumably through targeting B‑cell lymphoma 2 (Bcl‑2). In the present study, miRNA and protein expression levels were detected by reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. The cell proliferation and viability was measured using 3‑(4,5‑dimethylthiazol‑2‑yl)‑2, 5‑diphenyltetrazolium bromide and plate clonality assays, and the cell growth cycle was measured with a flow cytometer. Terminal deoxynucleotidyl transferase (TdT)‑mediated dUTP nick‑end‑labeling, Annexin V and caspase‑3 activity assays were performed to examine the cell apoptotic rates. The results showed that miR‑497 was markedly decreased, whereas Bcl‑2 was enhanced in MM tissues and cell lines. miR‑497 targeted Bcl‑2 and affected its downstream apoptosis‑related genes. The overexpression of miR‑497 promoted MM cell apoptosis through cell cycle arrest, and decreased colony genesis ability and viability. In addition, miR‑497 increased the sensitivity of MM cells to bortezomib. Taken together, miR‑497 suppressed MM cell proliferation and promoted apoptosis by directly targeting Bcl‑2 and altering the expression of downstream apoptosis‑related proteins. The combination of miR‑497 and bortezomib may enhance drug sensitivity, serving as a potentially available therapeutic method for MM.

Icariin protects against iron overload-induced bone loss via suppressing oxidative stress

Iron overload is common in patients with diseases such as hemoglobinopathies, hereditary hemochromatosis or elderly men and postmenopausal women. This disorder is frequently associated with bone loss and recently has been considered as an independent risk factor for osteoporosis. By excess reactive oxygen species (ROS) production through Fenton reaction, iron could induce osteoblast apoptosis, inhibit osteoblast osteogenic differentiation. Moreover, Iron could also promote osteoclasts differentiation and bone absorption. The goal of the study is to investigate whether icariin could reverse iron overload-induced bone loss in vitro and in vivo. Icariin is the major active ingredient of Herba Epimedii and has antioxidant, antiosteoporosis functions. In the current study, we demonstrated that oral administration of icariin significantly prevented bone loss in iron overloaded mice. Icariin could protect against iron overload-induced mitochondrial membrane potential dysfunction and ROS production, promote osteoblast survival and reverse the reduction of Runx2, alkaline phosphatase, and osteopontin expression induced by iron overload. Icariin also inhibited osteoclasts differentiation and function. Moreover, we also found that icariin remarkably reduced iron accumulation in bone marrow, suggesting that icariin has the ability to regulate systemic iron metabolism in vivo. These results indicated that icariin could be a potential natural resource for developing medicines to prevent or treat iron overload-induced osteoporosis.

Loading icariin on titanium surfaces by phase-transited lysozyme priming and layer-by-layer self-assembly of hyaluronic acid/chitosan to improve surface osteogenesis ability

Purpose

Icariin (ICA) is one of the main active constituents of Herba Epimedii for improving osteogenesis. It is necessary to create a simple and efficient method to load ICA onto the surface of titanium (Ti) implant. The purpose of this study was to establish a local ICA delivery system via a layer-by-layer (LbL) self-assembly system on phase-transited lysozyme (PTL)-primed Ti surface.

Materials and methods

A PTL nanofilm was first firmly coated on the pristine Ti. Then, the ICA-loaded hyaluronic acid/chitosan (HA/CS) multilayer was applied via the LbL system to form the HA/CS-ICA surface. This established HA/CS-ICA surface was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The ICA release pattern of the HA/CS-ICA surface was also examined. MC3T3-E1 osteoblast culture test and a rat model were used to evaluate the effects of the HA/CS-ICA surface in vitro and in vivo.

Results

SEM, XPS and contact angle measurement demonstrated successful fabrication of the HA/CS-ICA surface. The HA/CS-ICA surfaces with different ICA concentrations revealed a controlled release profile of ICA during a 2-week monitoring span. Osteoblasts grown on the coated substrates displayed higher adhesion, viability, proliferation and ALP activity than those on the polished Ti surface. Furthermore, in vivo histological evaluation revealed much obvious bone formation in the ICA-coated group by histological staining and double fluorescent labeling at 2 weeks after implantation.

Conclusion

The present study demonstrated that ICA-immobilized HA/CS multilayer on the PTL-primed Ti surface had a sustained release pattern of ICA which could promote the osteogenesis of osteoblasts in vitro and improve early osseointegration in vivo. This study provides a novel method for creating a sustained ICA delivery system to improve osteoblast response and osseointegration.

Icariin Reduces Cartilage Degeneration in a Mouse Model of Osteoarthritis and is Associated with the Changes in Expression of Indian Hedgehog and Parathyroid Hormone-Related Protein

Background

The aim of this study was to determine the role of icariin, a Chinese traditional herbal medicine extracted from Epimedium, in osteoarthritis (OA), using the murine anterior cruciate ligament transection (ACLT)-induced model of OA and micromass culture of murine chondrocytes.

Material/Methods

Twenty-four three-month-old C57/6J mice were randomly divided into three groups: the sham group (no surgery and joint injection with normal saline) (N=8); the ACLT + ICA group (ACLT surgery and icariin treatment) (N=8); and the ACLT group (ACLT surgery and joint injection with normal saline) (N=8). At 12 weeks after ACLT surgery, murine articular cartilage was harvested from all mice for histological evaluation of any differences in cartilage degeneration. In vitro micromass culture of mouse chondrocytes was used to study the effects of icariin on chondrocyte differentiation and growth from the three mouse groups.

Results

Icariin treatment (mice in the ACLT + ICA group) significantly reduced degeneration of cartilage in OA with increased cartilage thickness, associated with increased expression of collagen type II alpha 1 (COL2A1), decreased chondrocyte hypertrophy, and decreased expression of collagen type X (ColX) and matrix metalloproteinase 13 (MMP13). In vitro, icariin promoted chondrocyte differentiation by upregulating the expression of agrrecan, Sox9 and parathyroid hormone-related protein (PHrP) and down-regulation of Indian hedgehog (Ihh) and genes regulated by Ihh.

Conclusions

In a mouse model of OA icariin treatment reduced destruction of cartilage, promoted chondrocyte differentiation, upregulated expression of PHrP and down-regulated the expression of Ihh.

Icariin stimulates osteogenic differentiation and suppresses adipogenic differentiation of rBMSCs via estrogen receptor signaling

Icariin (ICA) is a major active ingredient in Herba epimedii, which is commonly used as a Chinese herbal medicine for the treatment of osteoporosis. Previous studies have revealed that ICA exerted a protective effect against bone loss and increased bone regeneration; however, the association between ICA and estrogen receptor (ER) signaling remains unclear. The aim of the present study was to determine the effect of ICA on rat bone marrow stromal cells (rBMSCs). Cell Counting Kit‑8 assays were conducted to measure proliferation, alkaline phosphatase (ALP) activity was evaluated to assess osteoblast differentiation, and reverse transcription‑quantitative polymerase chain reaction as well as western blotting were performed to detect the expression of cellular and molecular markers of osteogenic or adipogenic differentiation. The results demonstrated that treatment of rBMSCs with 10‑6 M ICA stimulated rBMSC proliferation and ALP activity. Furthermore, ICA treatment increased the expression of the osteogenic markers runt‑related transcription factor 2, collagen type 1 and bone morphogenetic Protein 2; however, it also decreased the expression of the adipogenic differentiation markers peroxisome proliferator‑activated receptor gamma and CCAAT/enhancer‑binding protein α. Treatment of rBMSCs with ICI182780, an ER antagonist, blocked the effects of ICA. Taken together, these findings indicated that ICA may stimulate osteoblast differentiation and inhibit adipogenic differentiation via the activation of the ER signaling pathway. Therefore, ICA has the potential to serve as a therapeutic alternative for the prevention and treatment of osteoporosis.

Flavonoid compound icariin enhances BMP-2 induced differentiation and signalling by targeting to connective tissue growth factor (CTGF) in SAMP6 osteoblasts

BACKGROUND

Icariin, a major active flavonoid glucoside, is widely used for the treatment of bone injury and rebuilding in the clinic because of its roles in suppressing osteoblastogenesis and promoting osteogenesis. The senescence-accelerated mouse SAMP6 was accepted as a useful murine model to reveal the mechanism of senile osteoporosis and the therapeutic mechanism of drug activity. However, little is known about the characteristics of SAMP6 osteoblasts and the associated regulatory roles of icariin.

METHODS

We isolated and cultured osteoblasts from SAMP6 or SAMR1 mice and compared their proliferation, migration, and differentiation by performing the CCK-8 assay, cell counting assay, EdU staining, cell cycle analysis, ALP staining and activity measurement, Alizarin red staining, and RT-qPCR analysis to measure the levels of osteoblast markers, including RUNX2, Colla1 and Oc. To assess the effects of icariin on BMP-2-induced osteoblast differentiation, after BMP-2 treatment, osteoblast markers were analyzed by RT-qPCR and semi-quantitative Western blotting. The effects of icariin on connective tissue growth factor (CTGF) were measured by RT-qPCR. shRNA targeting CTGF mRNA was employed to knockdown its expression level in osteoblasts.

RESULTS

The SAMP6 osteoblasts presented decreased the development and differentiation activity compared with SAMR1 osteoblasts, indicating that they are the potential mechanisms underlying age-associated disease. Moreover, SAMP6 osteoblasts presented upregulated CTGF compared with SAMR1 osteoblasts. Icariin enhanced BMP-2-induced osteoblast differentiation by downregulating CTGF expression, which tightly regulates osteoblast differentiation. By downregulating CTGF, icariin treatment upregulated phosphate-Smad1/5/8, indicating its activating effects on the BMP signaling pathway.

CONCLUSION

These results suggest that decreased osteoblast development and function potentially contributes to age-associated disease. Icariin exerts enhancing effects on BMP-2-mediated osteoblast development via downregulating CTGF.

Chinese single herbs and active ingredients for postmenopausal osteoporosis: From preclinical evidence to action mechanism

Postmenopausal osteoporosis is a systemic metabolic skeletal disease generally ascribable to a dearth of estrogen. Whether traditional Chinese medicine is effective in management of postmenopausal osteoporosis remains unclear. This article reviews the experimental evidence of both in vitro and in vivo preclinical studies with the theme of the application of Chinese single herbs and active ingredients in postmenopausal osteoporosis. It includes three single herbs (Herba Epimedium, Rhizoma Drynariae, and Salvia miltiorrhiza) and eight active ingredients (saikosaponins, linarin, echinacoside, sweroside, psoralen, poncirin, vanillic acid, and osthole). The experimental studies indicated their potential use as treatment for postmenopausal osteoporosis and investigated the underlying mechanisms including osteoprotegerin/receptor activator of nuclear factor κB ligand (OPG/RANKL), extracellular-signal-regulated kinase/c-Jun N terminal kinase/mitogen-activated protein kinase (ERK/JNK/MAPK), estrogen receptor (ER), bone morphogenetic protein (BMP), transforming growth factor (TGF)-β, Wnt/β-catenin, and Notch signaling pathways. This review contributes to a better understanding of traditional Chinese medicine and provides useful information for the development of more effective anti-osteoporosis drugs.

Icariin, but Not Genistein, Exerts Osteogenic and Anti-apoptotic Effects in Osteoblastic Cells by Selective Activation of Non-genomic ERα Signaling

Genistein and icariin are flavonoid compounds that exhibit estrogen-like properties in inducing bone formation and reducing bone loss associated with estrogen deficiency in both preclinical and clinical studies. However, the mechanisms that are involved in mediating their estrogenic actions in bone cells are far from clear. The present study aimed to study the signaling pathways that mediate the estrogenic actions of genistein and icariin in osteoblastic cells. The effects of genistein and icariin on the activation of estrogen receptor (ER) and the downstream mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway in murine osteoblastic MC3T3-E1 cells and rat osteoblastic UMR-106 cells were studied. As expected, genistein displayed higher binding affinity toward ERβ than ERα and significantly induced estrogen response element (ERE)-dependent transcription in UMR-106 cells in a dose-dependent manner. In contrast, icariin failed to bind to ERα or ERβ and did not induce ERE-dependent transcription in UMR-106 cells at 10^-10 to 10^-7 M. The effects of genistein (10 nM) and icariin (0.1 μM) on cell proliferation and differentiation in osteoblastic UMR-106 cells were abolished in the presence of ER antagonist ICI 182,780 (1 μM), MAPK inhibitor U0126 (10 μM), and PI3K inhibitor LY294002 (10 μM). Genistein at 10 nM rapidly induced ERK1/2 phosphorylation at 5–10 min in UMR-106 cells and the phosphorylation of ERα at both Ser118 and Ser167 in both MC3T3-E1 and transfected UMR-106 cells whereas icariin at 0.1 μM rapidly activated both ERK1/2 and Akt phosphorylation in UMR-106 cells and subsequent ERα phosphorylation at both Ser118 and Ser167 in MC3T3-E1 and transfected UMR-106 cells. Confocal imaging studies confirmed that the phosphorylation of ERα at Ser 118 and Ser 167 by genistein and icariin in MC3T3-E1 cells was mediated via MAPK- and PI3K-dependent pathway, respectively. Furthermore, our studies showed that icariin exerted stronger anti-apoptotic effects than genistein and 17β-estradiol (E2) and inhibited the cleavage of downstream caspase-3 in MC3T3-E1 cells induced by a potent PI3K inhibitor, PI828 (at 2 μM). These results indicated that the mechanisms that mediate the estrogenic actions of icariin in osteoblastic cells are different from those of genistein.

The Combination of icariin and constrained dynamic loading stimulation attenuates bone loss in ovariectomy-induced osteoporotic mice

Osteoporosis is a disease characterized by low bone mass and progressive destruction of bone microstructure, resulting in increasing the risk of fracture. Icariin (ICA) as a phytoestrogen shows osteogenic effects, and the mechanical stimulation has been demonstrated the improving effect on osteoporosis. The objective of this study was to investigate the effect of ICA in combination with constrained dynamic loading (CDL) stimulation on osteoporosis in ovariectomized (OVX) mice. The serum hormone levels, bone turnover markers, trabecular architecture, ulnar biomechanical properties, and the expression of osteoblast-related gene (alkaline phosphatase, ALP; osteocalcin, OCN; bone morphogenetic protein-2, BMP-2; Collagen I (α1), COL1; osteoprotegerin, OPG) and osteoclast-related genes (receptor activators of NF-κB ligand, RANKL; tartrate-resistant acid phosphatase, TRAP) were analyzed. The results showed that ICA + CDL treatment could increase the osteocalcin (20.85%), estradiol levels (20.61%) and decrease the TRAP activity (26.27%) significantly than CDL treatment. The combined treatment attenuated bone loss and biomechanical decrease more than single use of CDL treatment. ICA + CDL treatment significantly up-regulated the level of osteoblast-related gene expression and down-regulated the osteoclast-related genes expression; moreover, the combined treatment increased the ratio of OPG/RANKL significantly compared to ICA (72.83%) or CDL (65.63%) treatment alone. The present study demonstrates that icariin in combination with constrained dynamic loading treatment may have a therapeutic advantage over constrained dynamic loading treatment alone for the treatment of osteoporosis, which would provide new evidence for the clinical treatment of osteoporosis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1415-1424, 2018.

Oleanolic acid exerts bone protective effects in ovariectomized mice by inhibiting osteoclastogenesis

Postmenopausal osteoporosis (POP) is quite prevalent and many new drugs are under development to obtain better therapeutic outcomes. Oleanolic acid (OA) has been reported to prevent bone loss in ovariectomized (OVX) rats by stimulating osteoblastogenesis. One previous study has demonstrated that acetate of OA suppressed lipopolysaccharides (LPS)-induced bone loss in mice. However, the role of OA in the receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated osteoclastogenesis is still not elucidated. Here we show that OA dose-dependently inhibits RANKL-mediated osteoclastogenesis and the formation of functional osteoclasts without impairing the viability and osteoclastic potential in bone marrow macrophages (BMMs). Moreover, OA administration attenuates bone loss in OVX mice by inhibiting osteoclast's densities. Mechanistically, OA does not affect RANKL-induced activation of the NF-кB, JNK, p38, ERK and Akt pathways, but inhibits the expression of the nuclear factor of activated T-cells c1(NFATc1) and c-Fos. Moreover, OA significantly suppresses the expression of RANKL-activated osteoclast genes encoding matrix metalloproteinase 9 (MMP9), Cathepsin K(Ctsk), tartrate-resistant acid phosphatase (TRAP) and carbonic anhydrase II (Car2). This work has elucidated the molecular mechanism of OA in RANKL-mediated osteoclastogenesis and revealed the promising potential of OA to be further developed as a new drug to prevent and treat POP.

Icariin attenuates titanium particle-induced inhibition of osteogenic differentiation and matrix mineralization via miR-21-5p

Inhibition of bone regeneration by wear debris is the main cause of peri-prosthetic osteolysis. Here, we investigated the effect of icariin on cell proliferation, apoptosis, osteogenic differentiation and matrix mineralization of osteoblasts in an in vitro model of titanium (Ti) particle-induced osteolysis. In the present study, MC3T3-E1 cells were pretreated with 10^-8  M icariin for 4 h and then incubated with Ti particles (0.1 mg/mL). The results showed that Ti particles inhibited cell proliferation and promoted cell apoptosis of MC3T3-E1 cells, whereas icariin pretreatment blocked the effect of Ti particles. In addition, we found that icariin stimulation alone increased ALP activity, accelerated matrix mineralization and upregulated the levels of bone morphogenetic protein 2 (BMP2), Runt-related transcription factor 2 (Runx2), osteocalcin (OCN) and miR-21-5p; whereas, Ti particles alone exerted the opposite effects. Icariin partly reversed the effect of Ti particles on cell differentiation and mineralization. Twenty hours after transfection with antagomiR-21-5p or antagomiR-NC, the cells were pretreated with icariin for 4 h and then incubated with Ti particles. Further studies showed that partial knockdown of miR-21-5p abolished the promotion effect of icariin on osteoblast differentiation and matrix mineralization in Ti particle-stimulated MC3T3-E1 cells. In conclusion, miR-21-5p may be a potential pro-osteogenesis regulator and icariin may protect against Ti particle-induced inhibition of osteogenic differentiation and mineralization through upregulation of miR-21-5p.

Quercetin Stimulates Bone Marrow Mesenchymal Stem Cell Differentiation through an Estrogen Receptor-Mediated Pathway

Objectives

The present study aimed to investigate the overall effect of quercetin on mouse bone marrow mesenchymal stem cell (BMSC) proliferation and osteogenic differentiation in vitro.

Materials and Methods

BMSCs were treated with different concentrations of quercetin for 6 days. The effects of quercetin on cell proliferation were assessed at predetermined times using Cell Counting Kit-8 (CCK-8) assay. The cells were then treated with quercetin, estrogen, or an estrogen receptor (ER) antagonist (which was also administered in the presence of quercetin or estrogen) for 7 or 21 days. The effects of quercetin on BMSC osteogenic differentiation were analyzed by an alkaline phosphatase (ALP) assay kit, Alizarin Red S staining (ARS), quantitative real-time PCR (qPCR), and western blotting.

Results

The CCK-8 and ALP assays and ARS staining showed that quercetin significantly enhanced BMSC proliferation, ALP activity, and extracellular matrix production and mineralization, respectively. The qPCR results indicated that quercetin promoted osterix (OSX), runt-related transcription factor 2 (RUNX2), and osteopontin (OPN) transcription in the presence of osteoinduction medium, and the western blotting results indicated that quercetin enhanced bone morphogenetic protein 2 (BMP2), Smad1, Smad4, RUNX2, OSX, and OPN expression and Smad1 phosphorylation. Treatment with the ER inhibitor ICI182780 blocked the effects of quercetin.

Conclusions

Our data demonstrated that quercetin promotes BMSC proliferation and osteogenic differentiation. Quercetin enhances BMP signaling pathway activation and upregulates the expression of downstream genes, such as OSX, RUNX2, and OPN, via the ER.

Icariin promotes osteoblastic differentiation in OVX mice via MAPK signaling pathway revealed by profiling

Objective: Icariin (ICA), an extract from epimedium, has been reported to be effective in promoting bone formation. The objective of the study is to search for the molecular targets of ICA in bone mesenchymal stem cells (bMSCs) from the mice with ovariectomy (OVX)-induced osteoporosis.

Methods: Six-month-old Imprinting Control Region (ICR) mice that underwent OVX were treated with ICA. After three months, bone mass was evaluated by microcomputed tomography, morphometry and immunohistological detection. bMSCs were isolated from the femur and tibia to observe the self-renewal and differentiation capacities using colony-forming unit fibroblastic (CFU-F), colony-forming unit adipocyte (CFU-Adipo) and alkaline phosphatase (ALP) staining. In addition, microarray of bMSCs ex vivo was measured two weeks after ICA treatment and analyzed by heatmap and pathway analysis. The signaling pathway was further explored by western blot assay and inhibitors of p38 and ERK: SB203508 and PD98059.

Results: [Formula: see text]CT displayed a decrease in bone mass for three months after OVX. ICA treatment increased the trabecular thickness (Tb.Th), osteoblast number while decreased osteoclast number, elevating osteocalcin (OC) protein levels in vivo and facilitating the self-renewal and osteoblastic differentiation of bMSCs ex vivo. Microarray data indicated ICA rescued several gene expressions that were dysregulated by OVX. Pathway analysis revealed that the core genes acted by ICA were highly involved in MAPK signaling pathway. Further study demonstrated ICA suppressed ERK while stimulated p38 phosphorylation to promote osteoblastic differentiation in vitro.

Conclusion: ICA promotes osteoblastic differentiation of bMSCs in OVX mice. MAPK signaling pathway might be involved in the process.

Secretome analysis of rat osteoblasts during icariin treatment induced osteogenesis

Osteoporosis is a serious public health problem and icariin (ICA) is the active component of the Epimedium sagittatum, a traditional Chinese medicinal herb. The present study aimed to investigate the effects and underlying mechanisms of ICA as a potential therapy for osteoporosis. Calvaria osteoblasts were isolated from newborn rats and treated with ICA. Cell viability, apoptosis, alkaline phosphatase activity and calcium deposition were analyzed. Bioinformatics analyses were performed to identify differentially expressed proteins (DEPs) in response to ICA treatment. Western blot analysis was performed to validate the expression of DEPs. ICA administration promoted osteoblast viability, alkaline phosphatase activity, calcium deposition and inhibited osteoblast apoptosis. Secretome analysis of ICA-treated cells was performed using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. A total of 56 DEPs were identified, including serpin family F member 1 (PEDF), protein disulfide isomerase family A, member 3 (PDIA3), nuclear protein, co-activator of histone transcription (NPAT), c-Myc and heat shock protein 70 (HSP70). These proteins were associated with signaling pathways, including Fas and p53. Bioinformatics and western blot analyses confirmed that the expression levels of the six DEPs were upregulated following ICA treatment. These genes may be directly or indirectly involved in ICA-mediated osteogenic differentiation and osteogenesis. It was demonstrated that ICA treatment promoted osteogenesis by modulating the expression of PEDF, PDIA3, NPAT and HSP70 through signaling pathways, including Fas and p53.

The effect of icariin on bone metabolism and its potential clinical application

Osteoporosis is a bone disease characterized by reduced bone mass, which leads to increased risk of bone fractures, and poses a significant risk to public health, especially in the elderly population. The traditional Chinese medicinal herb Epimedii has been utilized for centuries to treat bone fracture and bone loss. Icariin is a prenylated flavonol glycoside isolated from Epimedium herb, and has been shown to be the main bioactive component. This review provides a comprehensive survey of previous studies on icariin, including its structure and function, effect on bone metabolism, and potential for clinical application. These studies show that icariin promotes bone formation by stimulating osteogenic differentiation of BMSCs (bone marrow-derived mesenchymal stem cells), while inhibiting osteoclastogenic differentiation and the bone resorption activity of osteoclasts. Furthermore, icariin has been shown to be more potent than other flavonoid compounds in promoting osteogenic differentiation and maturation of osteoblasts. A 24-month randomized double-blind placebo-controlled clinical trial reported that icariin was effective in preventing postmenopausal osteoporosis with relatively low side effects. In conclusion, icariin may represent a class of flavonoids with bone-promoting activity, which could be used as potential treatment of postmenopausal osteoporosis.

Fish bone peptide promotes osteogenic differentiation of MC3T3-E1 pre-osteoblasts through upregulation of MAPKs and Smad pathways activated BMP-2 receptor

Fish bone, a by-product of fishery processing, is composed of protein, calcium, and other minerals. The objective of this study was to investigate the effects of a bioactive peptide isolated from the bone of the marine fish, Johnius belengerii, on the osteoblastic differentiation of MC3T3-E1 pre-osteoblasts. Post consecutive purification by liquid chromatography, a potent osteogenic peptide, composed of 3 amino acids, Lys-Ser-Ala (KSA, MW: 304.17 Da), was identified. The purified peptide promoted cell proliferation, alkaline phosphatase activity, mineral deposition, and expression levels of phenotypic markers of osteoblastic differentiation in MC3T3-E1 pre-osteoblast. The purified peptide induced phosphorylation of mitogen-activated protein kinases, including p38 mitogen-activated protein kinase, extracellular regulated kinase, and c-Jun N-terminal kinase as well as Smads. As attested by molecular modelling study, the purified peptide interacted with the core interface residues in bone morphogenetic protein receptors with high affinity. Thus, the purified peptide could serve as a potential pharmacological substance for controlling bone metabolism.

Icariin inhibits LPS-induced cell inflammatory response by promoting GRα nuclear translocation and upregulating GRα expression

AIMS

Icariin (ICA) is a flavonoid isolated from certain plant species in the genus Epimedium, especially Epimedium brevicornum. Previous studies indicated that ICA has certain regulatory effects on some inflammatory diseases, and that ICA regulates the activity of glucocorticoid receptor (GR) and NF-κB. But the causal link between GR and NF-κB and other downstream pathways in effects of ICA remained elusive, therefore here we have investigated whether ICA could promote GR function, in turn, to regulate NF-κB and/or other factors to achieve its anti-inflammatory effect.

MAIN METHODS

Inflammatory cell models were induced by lipopolysaccharide (LPS) in RAW 264.7 and HeLa cell line. Observation of GRα nuclear translocation by confocal laser scanning microscopy. GRα and inflammatory cytokines expression was detected by RT-qPCR, Western Blotting and ELISA. Co-immunoprecipitation technique was used to detect the binding of GRα to downstream transcription factors. GRα activity was blocked by GRα antagonist RU486, and GR downstream transcription factors including NF-κB, c-Jun, and Stat3 were silenced by corresponding RNA interference.

KEY FINDINGS

In both inflammatory cell models, ICA decreased LPS-induced production of inflammatory cytokines (IL-6 and TNF-α). While ICA up-regulated the amount of GRα and promoted its nucleus translocation. The increased GRα in the nucleus by ICA bound more NF-κB, c-Jun, and Stat3. Blockade GRα and silence of NF-κB, c-Jun, and Stat3 expression partially abolished the anti-inflammatory effects of ICA.

SIGNIFICANCE

Promoted GR function and the consequent inhibition of pro-inflammatory transcription factors contribute a main mechanism by which ICA exerts its anti-inflammatory effect.

The flavonol glycoside icariin promotes bone formation in growing rats by activating the cAMP signaling pathway in primary cilia of osteoblasts

Icariin, a prenylated flavonol glycoside isolated from the herb Epimedium, has been considered as a potential alternative therapy for osteoporosis. Previous research has shown that, unlike other flavonoids, icariin is unlikely to act via the estrogen receptor, but its exact mechanism of action is unknown. In this study, using rat calvarial osteoblast culture and rat bone growth models, we demonstrated that icariin promotes bone formation by activating the cAMP/protein kinase A (PKA)/cAMP response element-binding protein (CREB) pathway requiring functional primary cilia of osteoblasts. We found that icariin increases the peak bone mass attained by young rats and promotes the maturation and mineralization of rat calvarial osteoblasts. Icariin activated cAMP/PKA/CREB signaling of the osteoblasts by increasing intracellular cAMP levels and facilitating phosphorylation of both PKA and CREB. Blocking cAMP/PKA/CREB signaling with inhibitors of the cAMP-synthesizing adenylyl cyclase (AC) and PKA inhibitors significantly inhibited the osteogenic effect of icariin in the osteoblasts. Icariin-activated cAMP/PKA/CREB signaling was localized to primary cilia, as indicated by localization of soluble AC and phosphorylated PKA. Furthermore, blocking ciliogenesis via siRNA knockdown of a cilium assembly protein, IFT88, inhibited icariin-induced PKA and CREB phosphorylation and also abolished icariin's osteogenic effect. Finally, several of these outcomes were validated in icariin-treated rats. Together, these results provide new insights into icariin function and its mechanisms of action and strengthen existing ties between cAMP-mediated signaling and osteogenesis.

Icariin ameliorates dexamethasone‑induced bone deterioration in an experimental mouse model via activation of microRNA‑186 inhibition of cathepsin K

The present study aimed to investigate bone deterioration in glucocorticoid‑induced osteoporosis (GIOP) mice, and the anti‑osteoporosis effect and underlying molecular mechanism of icariin. Dexamethasone (DSM) treatment was demonstrated to facilitate the induction of hypercalciuria in GIOP mice. Icariin treatment reversed the dexamethasone (DXM)‑induced disequilibrium of calcium homeostasis and bone resorption, and increased serum alkaline phosphatase, tartrate resistant acid phosphatase, osteocalcin and deoxypyridinoline. Haematoxylin and eosin staining revealed an increase in disconnections and separation in the trabecular bone network of the tibial proximal metaphysis, in the GIOP group. Icariin treatment reversed the DXM‑induced trabecular deleterious effects, and stimulated bone remodeling in GIOP mice. Furthermore, the results demonstrated that the mRNA and protein expression of cathepsin K were significantly increased in GIOP mice, compared with the control group. Icariin treatment may suppress the expression of cathepsin K in the tibia of GIOP mice. The levels of microRNA (miR)‑186 were markedly reduced in the tibia of GIOP mice compared with control group; however, this was inhibited by icariin treatment. Bioinformatics analysis demonstrated that miR‑186 regulates cathepsin K via binding to the upstream 3'‑untranslated region. Furthermore, transfection with miR‑186 mimics resulted in inhibition of cathepsin K expression, whereas miR‑186 inhibitors facilitated cathepsin K expression in osteoclasts. In conclusion, the present study demonstrated the protective effects of icariin against bone deteriorations in the experimental GIOP mice, and the underlying mechanism was mediated, at least partially, via activation of miR‑186‑mediated suppression of cathepsin K. These results provide evidence to support the use of icariin as a therapeutic approach in the management of glucocorticoid‑induced bone loss, and the disequilibrium of calcium homeostasis.

Porous composite scaffold incorporating osteogenic phytomolecule icariin for promoting skeletal regeneration in challenging osteonecrotic bone in rabbits

Steroid-associated osteonecrosis (SAON) often requires surgical core decompression (CD) in the early stage for removal of necrotic bone to facilitate repair where bone grafts are needed for filling bone defect and avoiding subsequent joint collapse. In this study, we developed a bioactive composite scaffold incorporated with icariin, a unique phytomolecule that can provide structural and mechanical support and facilitate bone regeneration to fill into bone defects after surgical CD in established SAON rabbit model. An innovative low-temperature 3D printing technology was used to fabricate the poly (lactic-co-glycolic acid)/β-calcium phosphate/icariin (PLGA/TCP/Icariin, PTI) scaffold. The cytocompatibility of the PTI scaffold was tested in vitro, and the osteogenesis properties of PTI scaffolds were assessed in vivo in the SAON rabbit models. Our results showed that the fabricated PTI scaffold had a well-designed biomimic structure that was precisely printed to provide increased mechanical support and stable icariin release from the scaffold for bone regeneration. Furthermore, our in vivo study indicated that the PTI scaffold could enhanced the mechanical properties of new bone tissues and improved angiogenesis within the implanted region in SAON rabbit model than those of PLGA/TCP (PT) scaffold. The underlying osteoblastic mechanism was investigated using MC3T3-E1 cells in vitro and revealed that icariin could facilitate MC3T3-E1 cells ingrowth into the PTI scaffold and regulate osteoblastic differentiation. The PTI scaffold exhibited superior biodegradability, biocompatibility, and osteogenic capability compared with those of PT scaffold. In summary, the PTI composite scaffold which incorporated bioactive phyto-compounds is a promising potential strategy for bone tissue engineering and regeneration in patients with challenging SAON.

Evaluation of synergistic osteogenesis between icariin and BMP2 through a micro/meso hierarchical porous delivery system

BMP2 is well known as an outstanding growth factor for inducing new bone formation. However, improvements are still required to use BMP2 effectively and expand its clinical application due to the potential side effects at high doses. In this study, icariin (IC), a type of traditional Chinese medicine, was originally proposed to be a cooperative factor for BMP2. An alkaline phosphatase (ALP) activity assay showed that IC promoted BMP2 osteogenesis in a concentration-dependent manner with significant enhancement at 38.4 µM versus that for BMP2 at 0.8 µg/mL. Furthermore, we developed a composite hierarchical porous scaffold (SF/SBA15; composed of micropores of silk fibroin [SF] scaffold and mesopores of SBA15) for the controlled delivery of BMP2 and IC. This composite scaffold was investigated by a series of physical characterizations and displayed good in vitro cell biocompatibility. In addition, the composite scaffold also showed the degradation rate of 12% dry weight loss and a slight change in the microstructures within 10 days. Moreover, BMP2 and IC were loaded into the SF and SBA15 structures, respectively, of the SF/SBA15 scaffold. This protein/drug loading system (SFBMP2/SBA15IC) provided delivery of BMP2 with an initial burst release of 60.9%±0.9% in the first 24 hours and a gradual release over the subsequent 6 days to 97.9%±0.8%, whereas IC exhibited a burst release of 64.2%±0.7% in the first 24 hours, followed by a sustained release to 92.4%±0.8% over 10 days. With the prolonged local retention and interaction duration of BMP2 and IC, the SFBMP2/SBA15IC scaffold provided better osteogenic differentiation than other groups with different loading modes of BMP2 or IC, as determined by ALP staining and quantitation and Alizarin red staining. Finally, the results of quantitative real-time polymerase chain reaction analysis indicated that the SFBMP2/SBA15IC scaffold induced a significantly higher increase in the RUNX2, ALP, COL I, and OCN expression levels of cocultured bone marrow mesenchymal stem cells than other payload composite scaffolds. This study suggests that a micro/meso hierarchical porous delivery system of BMP2 and IC ensures osteogenic synergy and demonstrates promise for bone tissue engineering.

Intracellular signaling pathways of inflammation modulated by dietary flavonoids: The most recent evidence

Dietary flavonoids, which occur in many plant foods, are considered as the most active constituents among the plant-derived ones in vitro and in vivo. To date, many studies have addressed the anti-inflammatory activity of flavonoids. However, their considerable structural diversity and in vivo bioavailability make them able to modulate different signaling pathways. The present review attempted to summarize and highlight a broad range of inflammation-associated signaling pathways modulated by flavonoids. Finally, based on the current scientist's literature, structure-activity relationships were concluded. Dietary flavonoids have the ability to attenuate inflammation by targeting different intracellular signaling pathways triggered by NF-κB, AP-1, PPAR, Nrf2, and MAPKs. Identification of the main structural features required for the modulation of these inflammation-related pathways (hydroxylation pattern, C2=C3 double bond) have an important role to play in the development of new anti-inflammatory drugs.

Psoralen stimulates osteoblast proliferation through the activation of nuclear factor-κB-mitogen-activated protein kinase signaling

Osteoporosis is a systemic skeletal disease that leads to increased bone fragility and susceptibility to fracture. Approximately 50% of postmenopausal women develop osteoporosis as a result of postmenopausal estrogen deficiency. To reduce fractures related to osteoporosis in women, previous studies have focused on therapeutic strategies that aim to increase bone formation or decrease bone resorption. However, pharmacological agents that aim to improve bone fracture susceptibility exhibit side effects. Current studies are investigating natural alternatives that possess the benefits of selective estrogen receptor modulators (SERMs) without the adverse effects. Recent studies have indicated that phytoestrogen may be an ideal natural SERM for the treatment of osteoporosis. In Chinese herbal medicine, psoralen, as the predominant substance of Psoralea corylifolia, is considered to be a phytoestrogen and is used as a remedy for osteoporosis. A number of studies have demonstrated the efficacy of psoralen in bone formation. However, the pathways and underlying molecular mechanisms that participate in psoralen-induced osteoblast formation are not well understood. In the present study, hFOB1.19 cells were treated with psoralen at different concentrations (0, 5, 10, 15 and 20 µM) for 0, 24, 36, 48 and 72 h, respectively. Reverse transcription-quantitative polymerase chain reaction and western blot assays were performed to detect glucose transporter 3 (GLUT3) expression. A cell counting kit-8 assay was used to analyze cell proliferation. In addition the effects of mitogen activated protein kinase inhibitors on extracellular signal-regulated kinase (ERK), phosphorylated (p)-ERK, p38, p-p38, c-Jun N-terminal kinase (JNK) and p-JNK expressions and cell proliferation were measured, as was the effect of nuclear factor (NF)-κB inhibitor on P65 and GLUT3 expressions and cell proliferation. The results indicated that psoralen stimulates hFOB1.19 cell proliferation in a dose-dependent manner (P<0.05). Phospho-ERK, p38 and JNK were markedly increased by psoralen compared with the control group (P<0.05), and the specific inhibitors of ERK (SCH772984), p38 (SB203580) and JNK (SP600125) reversed the stimulatory effects of psoralen on signal marker phosphorylation (P<0.05). The rate of psoralen-induced cell proliferation was significantly suppressed by inhibitors of ERK, JNK and p38 compared with psoralen treatment alone (P<0.05). In addition, psoralen stimulated osteoblast proliferation via the NF-κB signaling pathway. Therefore, the present findings suggest that psoralen may be a potential natural alternative to SERMs in the treatment of osteoporosis and fractures.

Molecular signaling mechanisms behind polyphenol-induced bone anabolism

For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.

Evaluation of Osteogenesis and Angiogenesis of Icariin in Local Controlled Release and Systemic Delivery for Calvarial Defect in Ovariectomized Rats

Typically, bone regenerative medicine is applied to repair bone defects in patients with osteoporosis. Meanwhile, there is an urgent need to develop safe and cheap drugs that induce bone formation. Icariin, which is reported to promote the osteogenesis of stem cells in vitro, is the main active component of Herba Epimedii. However, whether icariin could repair bone defects caused by osteoporosis remains unknown. In this study, an osteoporosis model in rats was established by an ovariectomy first, and then, the osteogenic and angiogenic differentiation of bone mesenchymal stem cells (BMSCs) treated with icariin was evaluated. Furthermore, calcium phosphate cement (CPC) scaffolds loaded with icariin were constructed and then implanted into nude mice to determine the optimal construction. To evaluate its osteogenic and angiogenic ability in vivo, this construction was applied to calvarial defect of the ovariectomized (OVX) rats accompanied with an icariin gavage. This demonstrated that icariin could up-regulate the expression of osteogenic and angiogenic genes in BMSCs. Meanwhile, osteoclast formation was inhibited. Moreover, CPC could act as a suitable icariin delivery system for repairing bone defects by enhancing osteogenesis and angiogenesis, while the systemic administration of icariin has an antiosteoporotic effect that promotes bone defect repair.

Alpinumisoflavone inhibits osteoclast differentiation and exerts anti-osteoporotic effect in ovariectomized mice

Alpinumisoflavone (AIF), a naturally occurring flavonoid compound exacted from Derris eriocarpa, has been found to have a number of pharmacological activities. However, its role in bone disorder has not been investigated. The aim of this study is to evaluate the osteoprotective effect of AIF on ovariectomy-induced bone loss in mice model and related underlying mechanisms. Our study provides experimental evidence that AIF could regulate the remodeling process of bone and exert osteoprotective effect against ovariectomy-induced bone loss. Moreover, our results show that AIF suppresses osteoclast differentiation by attenuating RANKL-induced activation of p38, ERK and JNK pathways and consequently represses the expression of c-Fos and NFATc1.